Abstract
Optical nanotapers fabricated by tapering optical fibers have attracted considerable interest as an ultimate platform for high-efficiency light-matter interactions. While previously demonstrated applications relied exclusively on the low-loss transmission of only the fundamental mode, the implementation of multimode tapers that adiabatically transmit several modes has remained very challenging, hindering their use in various emerging applications in multimode nonlinear optics and quantum optics. Here, we report the realization of multimode submicron tapers that permit the simultaneous adiabatic transmission of multiple higher-order modes including the LP02 mode, through introducing deep wet-etching of conventional fiber before fiber tapering. Furthermore, as a critical application, we demonstrate fundamental-to-fundamental all-fiber third-harmonic generation with high conversion efficiencies. Our work paves the way for ultrahigh-efficiency multimode nonlinear and quantum optics, facilitating nonclassical light generation in the multimode regime, multimode soliton interactions and photonic quantum gates, and manipulation of the evanescent-field-induced optical trapping potentials of atoms and nanoparticles.
Highlights
Optical nanotapers fabricated by tapering optical fibers have attracted considerable interest as an ultimate platform for high-efficiency light-matter interactions
As an immediate and critical application of the multimode adiabatic submicron tapers (MASTs), we demonstrate the fundamentalto-fundamental all-fiber third-harmonic generation (THG) with high conversion efficiencies >10−4, which was theoretically studied in a couple of proposals[28,36] but has been far from successful yet
An ultimate limitation in implementing MASTs with tapering conventional optical fiber is that higherorder modes (HOMs) become very close to each other in terms of effective index right after they are transformed into the cladding modes at the taper transition
Summary
Optical nanotapers fabricated by tapering optical fibers have attracted considerable interest as an ultimate platform for high-efficiency light-matter interactions. These properties have enabled broader-thanoctave-spanning supercontinuum generation[15], optical excitation of strongly confined coherent acoustic phonons[16,17], and creation of correlated photon pairs via spontaneous four-wave mixing[18,19] While these experiments were demonstrated using the light guided in the fundamental LP01 mode only, several emerging applications can be facilitated exclusively by utilizing the higherorder modes (HOMs), as they allow access to substantially broad landscapes of optical dispersion for intermodal phase-matching of multimode nonlinear and quantum optical processes and engineering of the evanescent field patterns for controlling the spatial profiles of optical trapping potentials. OMNTs that adiabatically transmit the LP01 and the LP11 modes only, relying on the use of specially designed fiber with a reduced cladding[32,33] or an unconventional index distribution[34,35]
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